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The above mechanism considered crystallization from the melt, which is important for injection molding of plastic components. Another type of crystallization occurs upon extrusion used in making fibers and films. In this process, the polymer is forced through, e.g., a nozzle that creates tensile stress which partially aligns its molecules. Such ...
Crystallization is the process by which solids form, where the atoms or molecules are highly organized into a structure known as a crystal.Some ways by which crystals form are precipitating from a solution, freezing, or more rarely deposition directly from a gas.
At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at a standard pressure such as 1 atmosphere or 100 kPa. When considered as the temperature of the reverse change from liquid to solid, it is referred to as the freezing point or crystallization point.
Crystallization; Crystal growth; Recrystallization; Seed crystal ... Recrystallization temperature is typically 0.3–0.4 times the melting point for pure metals and ...
This process of draining helps to separate the pure crystals from the impure liquid. Sweating: This phase is a controlled partial melting process. It further purifies the product by melting only a small portion of the crystal. The melting causes the impurities trapped within or between the crystal structures to be released and separated.
The Lindemann criterion states that melting occurs because of "vibrational instability", e.g. crystals melt; when the average amplitude of thermal vibrations of atoms is relatively high compared with interatomic distances, e.g. <δu 2 > 1/2 > δ L R s, where δu is the atomic displacement, the Lindemann parameter δ L ≈ 0.20...0.25 and R s is ...
Most liquids freeze by crystallization, formation of crystalline solid from the uniform liquid. This is a first-order thermodynamic phase transition, which means that as long as solid and liquid coexist, the temperature of the whole system remains very nearly equal to the melting point due to the slow removal of heat when in contact with air, which is a poor heat conductor.
During the process of fractional crystallization, melts become enriched in incompatible elements. [14] Hence, knowledge of the crystallization sequence is critical in understanding how melt compositions evolve. Textures of rocks provide insights, as documented in the early 1900s by Bowen's reaction series. [15]